The critical dimensions of bodies in unsteady thermal conductivity problems

The heating of plate, cylindrical and spherical shaped bodies in heat bearing media was considered, arriving at equations for the effectiveness of heating (amounts of heat absorbed). The use of the equations is illustrated by an example of heating quasi-spherical particles of iron powder in a layer of pseudo-liquefied corundum; the particle size with which the heat absorbed is minimum is found. As particle size increases, heating becomes rapidly less effective. The concept of the critical size of a body should be used in selecting the optimum heating conditions. Assimilation of heat is lowest with low values of the Fourier criterion.